[Issue 14708] New: destructor for temporary not called during stack unwinding

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14708

          Issue ID: 14708
           Summary: destructor for temporary not called during stack
                    unwinding
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Windows
            Status: NEW
          Keywords: wrong-code
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: k.hara.pg at gmail.com

Reduced test case:

extern(C) int printf(const char*, ...);

bool dtor = false;

struct S
{
    int n;

    void* get(void* p = null)
    {
        return null;
    }

    ~this()
    {
        printf("dtor\n");
        dtor = true;
    }
}

S makeS(int n)
{
    return S(n);
}

void foo(void* x)
{
    throw new Exception("fail!");
}

void test(int len = 2)
{
    foo(makeS(1).get());
    // A temporary is allocated on stack for the
    // return value from makeS(1).
    // When foo throws exception, it's dtor should be called
    // during unwinding stack, but it does not happen in Win64.
}
void main()
{
    try
    {
        test();
    } catch (Exception e) {}
    assert(dtor);   // fails!
}


I confirmed the issue on Win64, but I think it would happen in all platforms
excepting Win32.

Currently dmd handles the destructor calls for temporaries by using OPdctor and
OPddtor. It works correctly for Structural Exception Handling (SEH) in Win32.

On the other hand, Win64 and other Posix platforms generate exception handler
tables and use them from druntime. However dmd generates them only for the
explicit try-catch and try-finally statements, and doesn't recognize the
implied try-block between OPdctor and OPddtor elements.

By that, throwing exception from 'foo' skips dtor call for the temporary in
test().


It's an obstacle to my compiler fix for issue 14696.
https://github.com/D-Programming-Language/dmd/pull/4749

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